1. Field of the Invention
The present invention relates to resist useful for forming a fine resist pattern.
2. Description of the Related Art
Resist is widely used in the planar processes to manufacture semiconductor devices such as LSIs. In recent years, electronic devices capable of performing more functions with higher efficiency have been developed, incorporating ICs which have very high integration densities. To manufacture such high integration density ICs, resist patterns which have not only sufficient fineness and but also enough heat-resistance for being able to endure reactive ion etching (RIE) must be used. Hence, there is a demand for a resist which has high resolution and heat resistance.
Published Unexamined Japanese Patent Applications 62-25349 and 61-164740 disclose a resist which has sufficient heat resistance and resolution. The higher the p-cresol content of the resist, the higher the resolution. However, if the resist contains an excessive amount of p-cresol, its alkali-solubility and its molecular weight will decrease. In this case, the resist has neither sufficient photosensitivity nor sufficient heat-resistance. Therefore, a composition or an efficiency of the resist is limited. In addition, when these resists are exposed to ionizing radiations, a crosslinking reaction occurs, and sensitivity of the resists used as positive-type resists is lowered.
The conventional negative-type resist has but a relatively low heat resistance. Nor does it have sufficient transparency; it in fact absorbs a considerable amount of light. Hence, especially when exposure is performed by using light having short wavelengths, light applied to a layer of this conventional resist, formed on a semiconductor substrate, cannot reach the surface of the layer which is in contact with the substrate. As a consequence, only a low-profile resist pattern can be obtained.